WENN- Mariah Carey's manager has hit back at criticism of the star from a former employee who described the singer's recent performances as "lackluster".

Last month footage emerged online of the singer whistling to her song "I Know What You Want" at a performance during her Las Vegas residency at Caesars Palace, which began in May 2016 and ended on July 18.

In the clip, Mariah's 2002 track with Busta Rhymes can be heard playing in the background, though rather than singing, the Grammy Award winner is seen whistling along to part of the track while moving her arms to the music.

And during her tenure, audience members voiced disappointment over her lackluster performances, with videos showing Mariah, 47, putting little effort into her dance routines.

In an interview with Complex magazine on Wednesday, the singer's former choreographer and creative director Anthony Burrell, who was fired after her disastrous New Year's Eve performance on "Dick Clark's Rockin' New Year's Eve," said his previous boss has given up on live performances.

"It’s just typical Mariah. Mariah is clear. When she doesn’t wanna do something, she doesn't do it," Burrell told Complex. "She's performing with lackluster and no f**ks given, and it's taking away her star."

Manager Stella Bulochnikov has now hit back at the choreographer, who was featured in the star's docu-series Mariah's World, calling him "bitter" and defending the star, who she says has "worked non-stop".

"Why don’t you come watch MC perform to sold out crowds three times a week for yourself and see what you think instead of giving a former disgruntled employee’s bitter comments life," she told website TooFab on Thursday.

The protective manager also posted a picture of her famous charge on Instagram on Friday with the caption: "#exquisite #breathtaking #superstar #legend I'm so honored to call you my #client my #friend #sisters #eternally #girlfriends #protect #love #empower each other #godbless."

Burrell was fired by the Dreamlover star following her appearance on the New Year's Eve show after she was heavily criticized for a performance which saw her stop singing and dancing when she began experiencing technical difficulties as pre-recorded vocals continued to play.

Burrell is now working as a dancer and choreographer for Beyonce's company Parkwood Entertainment.